Total brain white matter is a major determinant of IQ in teens born preterm

It is well-known that preterm
children have a higher rate of learning difficulties and lower average IQ
scores compared to their full-term peers, but until now the underlying brain
differences associated with these problems were not known.

Gemma Northam and colleagues at the
UCL Institute of Child Health followed up a group of preterm children as
teenagers and used novel imaging techniques to look for any differences in
their brains compared to healthy volunteers. The study, funded by Action
Medical Research, focussed on the brain’s “white matter” which is made up of
fibres running between nerve cells, connecting different parts of the brain.

The authors showed that IQ score
and performance in final school exams (GCSEs) were best predicted by the total volume
of white matter in the brain, irrespective of the presence or severity of other
brain abnormalities detected on MRI scans.

Dr Northam explains: “This is a
surprising finding. Our results show that differences in the amount of white
matter accounted for 70% of the variability in IQ score in these children”

The researchers suggest that this may be a consequence of premature
birth during the late second and early third trimester of pregnancy, which is
known to be a critical time for the establishment of white matter connections between
brain regions (see image).

The authors comment: “These
findings emphasise the need for early therapeutic efforts to promote the
development of cerebral white matter in preterm infants and indicate that such
interventions may lead to real-world improvements in IQ and academic
performance in this expanding patient group”.

Images: Brain white matter connections in 3 different teenagers who were
born prematurely – shown on diffusion-weighted MRI scans